Art of refining metals



June 22, 1937. I M. F. w. HEBERLEIN" 2,084,394

ART OF REFINING METALS Filed Feb. 8, 1955 I LEACH WITH CAUST/C 500/! RES/DUE L/ uo Q -R 7a, Cu, Ag anaAu I NEUTRAL/2E PREC/P/TATE WITH H 50 SOME Se, Cu, Te and Pb EACH H2 504 I r I LIQUOR LEACH WITH RES/DUE LIQUOR RES/DUE WITH 56 0 H 80 TO LEAD Te and Cu 4 .7.? and/1L4 SMELTER- V I To .SELEN/UM I PREC/P/TATE DORE RECOVERY PLANT LIQUOR 58,72 and WITH Fe FUR/VA c5.

, 7k-cu CEMENT ROAST AT 600!- fifiji ygi 0 TELLUP/L/M 700, "0/550LVE \M fLANT Te //V NaOH and RECOVER IN I I 032/41. MANNEP LIQUOR 5e PREC/PITATE Te, 04 I To .SELEN/UM To TELLUR/UM 62/ andl-e Escovsxev PLANT RECOVERY PLANT T0 Cu SMELTER INVENTOR Heberlein BY ATTORN Yd Patented June 22, 1937 UNITED STATES PATENTVOFHFICE I 2,0a4,394- I The American Metal Company, Limited, New York, N. Y., a corporation of New York Claims.

This is an invention for the treatmentof slimes produced in the electrolytierefining of'copper and, more particularly, the invention relates to the removal from the slimes of impurities such I of the invention will become apparent from the a ing, anodes.

following detailed description.

The invention further resides in the method, features and novel series of steps of the character hereinafter described and claimed.

For an understandingof the invention, reference is to be had to the follo'wingdescription and to the sheet of drawings which constitutes a diagrammatic representation of the novel series of steps of the invention.

Only small amounts of selenium and tellurium are eliminated in the furnace operation of makand tellurium pass, with other impurities including the precious metals and some copper, into the slimes. When treating these slimes for the reclamation of-the precious metals, small amounts of selenium and tellurium do not complicate the substantially such as described by L. Addicks Copper Refining (First Edition McGraw Hill Book Company, Incl, 1921) on page 119.. .But- J when the amounts of selenium and tellurium are.

appreciable, they cause considerable dimculty when treated this way, and if it is intended to recover selenium and/or tellurium as commercial by-products, the recoveries are low.

The roast-leach process heretofore practiced involves roasting of the slimes to make coppersoluble and then leaching withsulphuric acid "to eliminate the copper. tellurium are volatilized in the roasting and are partially recovered in the flue system; some are dissolved in the acid leach and as this solution is either returned to the tankhouse, or used to manufacture bluestone, selenium and tellurium are harmful and must be eliminated.

I have made a careful study of the constitution of tankhouse slimes which is described in Metall und Erz for 1933, vol. 30, pages 363-366 en titled "Ueber die Enti'ernung von Selen und Tellur aus Kupfer-Electrolysen-schlaemmen.

The most important constituents are metallic During the electrolysis selenium Some of the selenium and application February a, 1935, Serial No. 5,515

copper, cuprous selenide (CuzSe), cupric selenide. (CuSe) silver telluride (AgaTe), lead, silver and gold.

From my observations, when conducting the roasting in accordance with'my invention at a temperature between 600 and 800 F., I find the following reactions take place:

The completeness of these reactions depends very much upon the handling of the roasting furnace and after a practical roast, according to my method, the selenium in the calcines should be present principally asv 2CuO.SeO2 ,or CuO.SeOz and the tellurium as TeOi.

In accordance with my invention and in order to accomplish a satisfactory calcine, I first thoroughly wash the slimes free of sulphuric acid and copper sulphate. After drying, the material is carefully roasted preferably at 600-680 F. with or without rabbling and preferably in a muille roasting furnace, the best results having been obtained when the greatest heat is appliedto the bottom of the muflle, and the draft being regulated to withdraw rapidly any fumes produced.

be controlled by regulation of the'draft to control the amount of fresh air allowed to come in contact with the slimes. I find that when the slimes are roasted in thin layers, the best results are obtained because the danger of overheating is avoided. Layers of about one inch thick roast satisfactorily, but I do not wish to be limited to this thickness as the thickness will vary with the kind of slimes being treated. When the slimes are not fresh, i. e., such as have become oxidized, I find that more heat must be applied.

A satisfactory roast may be judged by the amount of sulphuric acid insoluble copper in the calcines which should be less than 0.3%. The slimes oalcine should also have a yellow green color, thus indicating a mixture of green copper selenites and yellow tellurium tri-oxides.

After roasting, the calcines are leached with a solution of caustic soda for the purpose of dissolving the selenium. A solution containing that from 2 /2 to 10% of Na(OH) is suitable, Sumcient heat is applied to bring the mass to the boiling point. The amount of caustic soda used depends upon the amount of selenium and lead in the material, as some lead is also soluble. The liquor from this operation is neutralized with .sulphuric acid, producing a second liquor containing selenium dioxide and a precipitate containing small amounts .of copper and tellurium, some selenium, and the lead soluble in the caustic. 'Under roasting conditions, when the temperature is maintained at 600 F.-800 F. only small amounts of copper and tellurium will appear on neutralization. A larger amount of lead-is dissolved by the caustic soda and appears in the leach liquor.'- Theselenium liquor is worked up in the usual way for the production of metallic selenium. The precipitate is treated .with sulphuric acid producing a third liquor and a residue containing lead which is transferred to a lead smelter. This liquor is neutralized with soda ash and filtered. The filtrate contains selenium and is combined with the liquor mentioned above which is used for the production of metallic selenium; the precipitate contains,-

tellurium together with a trace of copper, this precipitate being transferred to the tellurium plant.

The residue from the original caustic soda leach contains, besides the copper and precious metal values of the originalslimes, the remainder of the tellurium. This is treated with sulphuric acid which dissolves the copper and the rabbled thoroughly at -l0-l5 minute intervals.

During this period no fumes were observed. The roasted material was then leached with caustic soda and sulphuric acidgas. described 'above, with the following results:

Distribution Contents, grams percentage Material Cu Se Tc Cu Se Te Raw slimes 20. 7 5. 2 5. 6 100 100 100 Oalcines 20. 7 5.13 5. 6 100 98. 6 100 NaOH liquor (A on chart)-.- 0.10 5.12 .5 98.4 Tr. HgSO; liquor (B on chart) 20. 6 3. 9 99. 5 69. 7 Final leach residue (0 on chart). l. 67 30. 3

It will be noted that the content of the selenium and tellurium in the roasted calcined slimes is such that substantially all of the selenium originally present in the copper slimes is still present. The selenium is present as copper selenite and tellurium as tellurium trioxide, as above mentioned. i

If the roasting should beconducted below 570 F., silver is oxidized and will go into solution with sulphuric acid when it is used to eliminate thecopper contained in the slimes; also telluride @will be oxidized according to the equation 2AgzTe+30z=2(Ag0.TeOz) which is soluble in caustic soda and consequently considerable amounts of tellurium will be soluble when it is used to dissolve the selenium and thus contaminate this solution.

The invention as heretofore described involves the steps of roasting the slimes while maintaining them in a predetermined temperature range and then leaching the calcines with caustic soda. This is preferred practice but it shall be understood that the invention is not to be thus limited. Thus, the roasting of the slimes while maintaining the temperature thereof in the range set forth in this specification, 1. e., 600 F.-800 F. is an advantageous first step over the prior art process of roasting the copper slimes and then leaching them with H2804. When the process herein described is used, there is less expensive Doroperation because the selenium and tellurium are eliminated and the greater proportion of the copper is recovered in the tankhouse instead of in the Dor slag.

While some slimes give a satisfactory result with a single-roast and caustic soda leach, Iilnd that when the slimes are not fresh, or when the selenium content is high-as for instance 20%,

a second roast under the same conditions as mentioned above, and leachi g a ain with caus- -tic soda, further increases the extraction of selenium.

While the invention has been described with respect to certain particular preferred examples which give satisfactory results, it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended therefore in the appended claims to cover all such changes and modifications.

What .is. claimed as new and desired to be secured by Letters Patent is:

1. In the'art of treating copper slimes containing selenium and tellurium, the step which consists in roasting the copper slimes at about, 600 to about 700 F. and somewhat-above substantially out-of contact with'heating gases and with intermittent rabbling, to form copper selenite and tellurium trioxide but at a temperature not to decompose or break down substantially these compounds. 2 In the art of treating copper slimes containing selenium and tellurium, the step which consists in roasting the copper slimes while disposed in thin layers at about 600 to about 700 F.

and somewhat above substantially out of contact with heating gases and with intermittent rabbling, to form copper selenite and tellurium trioxide but at a temperature not to decompose or break down substantially these compounds.

3. In the art of treating copper slimes containing selenium and tellurium, the steps which 1 consist in roasting the copper slimes to produce a selenite and tellurium tri-oxide, and leaching the resulting calcines with caustic soda.

4. In the art of treating copper slimes, the step which consists in leaching the calcined c'opper' consist in roasting the copper slimes while maintaining the temperature thereof in the range 600 F.800 F., and leaching the calcined copper.

slimes with caustic soda to obtain a liquor conaoagsoa taining mainly selenium and a residue containing the precious metals and substantially all of the tellurium and copper of.the original slimes, and leaching said residue with sulphuric acid to obtain a liquor containing tellurium and copper.

7. In the art of treating copper slimes, the steps which consist in leaching the calcined copper slimes containing a selenite and tellurium tri- -oxide with caustic soda to obtain a liquor containing mainly selenium and a residue containing the precious metals and substantially all of the tellurium and copper of the original slimes, leaching said residue with sulphuric acid to obtain a liquor containing tellurium and copper, and precipitating tellurium and copper from said liquor.

8. In, the art of treating copper slimes, the steps which consist in leaching the calcined copper slimes containing a selenite and tellurium trioxide with caustic soda to obtaina liquor containing mainly selenium and a residue containing theprecious metals and substantially all of the tellurium and copper of the original slimes, leaching said residue with sulphuric acid to obtain a liquor containing tellurium and copper, treating said liquor with metallic iron to precipitate tellurium and copper therefrom-and roasting said precipitate to separate the copper from the tellurium.

9. In the art of treating copp'er slimes, the steps.

which consist in leaching the calcined copper slimes containing a selenite and tellurium trioxide with caustic soda to obtain a liquor containing mainly selenium and a residue containing the precious metals and substantially all of the tellurium and copper or the original slimes, neutralizing said liquor with sulphuric acid to precip'itatea mixture containing selenium, tellurium and lead, and leaching said mixture with sulphuric acid tothereby obtain a liquor containing selenium and tellurium.

10. In the art of treating copper slimes, the

steps which consist in leaching the calcined copper slimes containing a selenite and tellurium tri-oxide' with caustic soda to obtain a liquor containing mainly selenium and a residue containing the precious metals and substantially all of the tellurium and copper of the original slimes,

neutralizing said liquor with sulphuric acid to precipitate a mixture containing selenium, tellurium and lead, leaching said mixture with sulphuric acid to obtain a liquor containing selenium and tellurium, leaching said residue with sulphuric acid to obtain a liquor containing tellurium and copper, and precipitatingtellurium and copper from said last named liquor.

11. In the art of treating copper slimes containing selenium and tellurium, the steps which consist in roasting the copper slimes while maintaining the temperature thereof in the range of 600 F.-800 F., leaching the calcined copper slimes with caustic soda to obtain a liquor containing mainly selenium and a residue containing the precious metals and substantially 'all of the tellurium and copper of the original slimes, neutralizing said liquor with sulphuric acid to precipitate a mixture containing selenium, tellurium and lead, leaching said mixture with sul-' phuric acid to obtain a liquor containing selenium and tellurium, leaching said residue with sulphuric acid to obtain a liquor containing tellurium and copper,jand precipitating tellurium and copper from said last named liquor.

12. In the art of refining metals, the steps which consist in treating a liquor containing tel-' lurium and copper with metallic iron to precipitate tellurium and copper therefrom, androasting said precipitate to prepare it for leaching out the copper from the tellurium.

13. In the art of refining metals, the steps which consist in treating a liquor containing tellurium and copper with metallic iron to precipitate tellurium and copper therefrom, roasting said precipitate to separate the copper from the telresulting calcines with caustic soda.

15. In the art of treating copper slimes containing selenium and tellurium, the step which copper slimes, the

consists in roasting the copper slimes at above approximately 600 F. substantially out of contact with heating gases and with intermittent rabbling until substantially all of the selenium originally present in the-copper slimes is present 'as, copper selenite and the tellurium is present as tellurium .trioxide.

Max F. w. mm. 

